Frequently Asked Questions

Arsenic in New Jersey well water is almost always naturally occurring.  It dissolves into groundwater from arsenic-bearing minerals in many of the bedrock aquifers of Northern and Central New Jersey.

  • Yes, if arsenic has been detected in your well water above the New Jersey Safe Drinking Water maximum contaminant level (MCL) of 5 micrograms per liter (mcg/L)
  • Arsenic is a toxic element. It is known that people who drink water containing elevated levels of arsenic have an increased risk of a wide range of adverse health effects.
    • Arsenic is known to greatly increase the risk of cancer in humans who drink water with elevated levels. Chronic exposure to high levels of arsenic is associated with a range of serious health problems including skin lesions, skin cancer, lung cancer, liver cancer and bladder cancer.
    • Arsenic exposure has also been associated with increased risk of cardiovascular disorders, neuropathy and diabetes. Studies show arsenic from drinking water has a negative effect on children's IQ.
  • When you sell your home, you will be required to test for arsenic and share the results with the buyer of your home. If the arsenic level is above the New Jersey arsenic standard of 5 mcg/L, a treatment system will be needed.
  • Even though the MCL for arsenic is 5 mcg/L in New Jersey, the US Environmental Protection Agency has set a maximum contaminant level goal of 0 mcg/l for arsenic in drinking water.
  • The maximum contaminant level goal (MCLG) is defined by USEPA as the level of contaminant in drinking water below which there is no known or expected risk to health and which allows a margin of safety. Because arsenic is a known human carcinogen via drinking water, the USEPA has determined that the maximum contaminant level goal is zero for arsenic in drinking water.
  • The MCLG is usually lower than the Maximum Contaminant Level (MCL). The MCL is the highest level of a contaminant that is legally allowed in drinking water.  MCLs are set as close as feasible to the MCLGs. For arsenic, the New Jersey MCL is 5 mcg/l. 
  • Surveyed treatment providers in New Jersey and the New Jersey Department of Environmental Protection recommend adsorption systems to treat arsenic in private wells.  The biggest decision buyers are faced with is whether to treat all the water in the house or a single tap in the kitchen.
  • The preferred system is a Whole-House treatment system with two tanks in series, which is often called "Point-of-Entry" (POE) because it treats all water in the home near the point where the water enters the home.
  • The other type of treatment is single tap treatment, which is often called "Point-of-Use" (POU) because the treatment unit is usually near the single tap used for drinking and cooking water.
  • In the case of a home sale, the buyer of the home should always choose the type of water treatment system and who will install it. This is important so the person living with the system will know what they have, how to monitor and maintain it, and who to call for service, because of course the buyer is the one who will be drinking the water.


POE Advantages:

  • All water in the house is treated
  • Can drink water safely from any tap
  • Arsenic-free shower and bath water
  • Can easily size system to maintain flows the same as before the treatment system was installed


POE Disadvantages:

  • Installation cost
  • Maintenance cost (about $1 a day)
  • The POE system is the most protective of you and your family's health.
  • All water in the house is treated so any tap in the home can be used safely for drinking water.
  • Water for bathing, showering, brushing teeth, and laundry will also be arsenic-free.
  • A New Jersey study found that Whole-House arsenic water treatment provided more effective exposure reduction than Point-of-Use treatment. See this link for an abstract of the study.

One-tank POE system disadvantages:

    • With no back-up/safety tank homeowners are at risk of drinking water with unhealthy levels of arsenic during the period after the arsenic begins to break through the treatment media and before the next testing.

One-tank POE system advantages:

    • Cheaper in the short term
  • A one-tank POE system is cheaper in the short term, but with no back-up/safety tank homeowners are at risk of drinking water with unhealthy levels of arsenic during the period after the arsenic begins to break through and before the next testing.
  • The water goes through the first tank and then through the second tank.  We call the first tank the "worker tank" because it does the most work removing arsenic. When the worker tank is new it will remove all the arsenic, but after about one year (depending on the arsenic level and how much water is used), the worker tank's arsenic removal efficiency will start to decline and some arsenic will start to break through the worker tank. When this occurs, the second tank will remove the arsenic, and this is why we call the second tank the "safety tank".
  • Without the safety tank you would be exposed to the arsenic getting through the worker tank.  With only a one-tank system you won't know you're being exposed to arsenic until the next water test is obtained.
  • A properly installed and maintained two-tank POE system will reduce your arsenic exposure to zero, which is the EPA maximum contaminant level goal for arsenic. A one-tank POE system can't meet this goal.
  • A two-tank POE system is also more economical over the life of the system. With one tank you'll need to change the tank as soon as the concentration gets near 5 mcg/l. Otherwise you will be exposed to arsenic levels above the state standard. However, with a two-tank POE system, you can safely conduct once per year sampling and not need to replace the worker tank until the concentration after the worker tank exceeds 5 mcg/l.  Even if the concentration after the worker tank goes up to 10 or 20 mcg/l, the safety tank will remove all of the arsenic before it reaches the taps in your home.
  • The typical two-tank POE arsenic water treatment system is 4-5 feet tall and requires a floor area of about 2 feet by 3 feet.
  • Most homeowners find space for these systems in their basement near the well water pressure tank.
  • The POE system has a higher initial cost but the New Jersey Housing and Mortgage Finance Agency offer no interest loans through its Potable Water Program to cover the cost of installation.
  • The POE system requires approximately 6 square feet of floor space in the basement, though it does not take up any space under the kitchen sink like a POU system would.

POU advantages:

  • When POU is used for a single tap, Installation cost is less for POU than for POE.
  • When POU is used for a single tap, maintenance cost is less for POU than for POE.

POU disadvantages:

  • Water from untreated taps still contains unhealthy levels of arsenic. 
  • Once the under the sink storage reservoir is depleted the flow volume will be down to a trickle until the storage reservoir fills back up with treated water, and this may take a couple of hours.
  • Some POU systems only remove Arsenic 5 (reverse osmosis).
  • POU systems usually do not have a safety tank so users will be exposed to arsenic contamination after the capacity is reached and before testing indicates the need for a replacement.
  • With a POU systen you will still be bathing, showering, brushing teeth, washing clothes and filling up swimming pools or hot tubs with arsenic-contaminated water.
  • Studies have shown that in homes with a single tap arsenic POU water treatment system, it is not uncommin for people to occasionally drink from untreated taps, and when they do, arsenic levels increase in their urine.                                                                                                                                                                                                                                                                                    
  • If POU treatment at the kitchen sink is used, the kitchen tap should be the only source of water used for drinking or cooking. If water may be used for drinking in other rooms of the home (e.g. at a bathroom sink), either a POU unit should be installed at each potential drinking water tap in the home or a Whole-House Point-of-Entry (POE) system should be used.
  • When the cost of multiple POU systems is considered, it often becomes more economical to install a Whole-House POE system.
  • Some local health departments require Whole-House POE arsenic water treatment to ensure the health of current and future homeowners
  • The following treatments are not effective for removing any arsenic:
    • Boiling water (this will increase the arsenic concentration)
    • Ultraviolet (UV) light
    • Cation exchange (commonly called a water softener)
    • Granular activated carbon (GAC)
    • Aeration
    • Magnetic water conditioners
    • Water filtration pitchers (Brita, etc.)
    • Water filtration from the refrigerator
    • Sediment filter
  • In New Jersey well water there are two common forms of arsenic that need to be removed by water treatment, Arsenic 3 and Arsenic 5.
  • Arsenic 3 is much more difficut to remove from well water than Arsenic 5 because Arsenic 3 has a neutral charge.
    • There is no simple and affordable test commercially available to determine which arsenic species is present so the species of arsenic present is usually unknown, though there is a rule of thumb which can help (See FAQ #15).
  • The New Jersey Geological and Water Survey estimates that 20% of New Jersey wells with arsenic above the Maximum Contaminant Limit (MCL) of 5 micrograms/liter (mcg/L) have significant concentrations of Arsenic 3. 
  • There is no simple and affordable test commercially available to determine which arsenic species is present so the species of arsenic present is usually unknown. 
  • There is an Arsenic Speciation "Rule of Thumb" developed by the New Jersey Geological and Water Survey and Rutgers University that can be used to determine if Arsenic 3 may be a factor or not.
  • The Arsenic Speciation Rule of Thumb works by answering these two questions:
    • Are the Iron or Manganese concentrations in the untreated well water greater than 50 micrograms/liter (mcg/L)?
    • Is the Dissolved Oxygen concentration in the untreated well water less than 1.0 milligrams/liter (mg/L)?
  • If the answer to each question is "no" it is very unlikely that the water contains a significant concentration of Arsenic 3. 
  • If the answer to either question is "yes" then Arsenic 3 is likely present at a concentration greater than 3 mcg/L and therefore a serious factor in water treatment selection. In this case, a confirmatory Arsenic 3 test by arsenic speciation cartridge or laboratory analysis is recommended before spending extra money on treatment components to convert Arsenic 3 to Arsenic 5.
  • Reverse Osmosis 
    • Reverse osmosis is not effective at removing Arsenic 3.  There is no simple and affordable test commercially available to determine which arsenic species is present so the species of arsenic present is usually unknown, though there is a rule of thumb which can help (see FAQ#15).
    • Reverse osmosis can be an effective Point-of-Use (POU) treatment system for drinking and cooking water when Arsenic 3 is not present
    • POU reverse osmosis has been found to be a good backup in combination with a Whole-House POE arsenic removal system when only Arsenic 5 is present.
    • Whole-House reverse osmosis is not recommended due to cost, size of system, and the fact that reverse osmosis treated water should not be run through copper plumbing.
  •  Anion Exchange Systems
    • Anion exchange systems are not effective at removing Arsenic 3. There is no simple and affordable test commercially available to determine which arsenic species is present so the species of arsenic present us usually unknown, though there is a rule of thumb which can help (see FAQ#15).
    • The anion exchange system requires regular maintenance that involves purchasing water softener salt to keep the brine tank filled. If the salt level is not maintained, the system will stop removing arsenic and will dump the previously removed arsenic into the home's water at a very elevated concentration.
    • When an anion exchange system runs through a regeneration cycle all of the arsenic captured by the system will be flushed out of the tank and discharged somewhere near the home, usually to the home's septic system.
    • For the above reasons, we strongly recommend against using anion exchange for arsenic removal even if only Arsenic 5 is present.
    • However, for well water with a high pH (pH>8.5), anion exchange can be an effective tool for lowering pH and can be used as pre-treatment in combination with a Whole-House Point-of-Entry (POE) arsenic removal system (see FAQ# 27).
  • It's important to realize that if you choose a less expensive arsenic treatment media it may have a lower capacity to absorb arsenic. This means you may need to replace the tanks more often and the system will likely cost you more over the long term.
  • DEP strongly recommends a 5-micron pre-treatment sediment filter to prevent any dirt or geologic materials coming up from the well from clogging or fouling the arsenic water treatment equipment. 
  • If a water softener or other treatment unit capable of removing dirt or other particles will be located before the arsenic water treatment unit, and the well water is not especially dirty, then the pre-treatment sediment filter can be considered optional.
  • A 5-micron size post-treatment sediment filter is essential to prevent any particles of treatment media, which may be highly enriched in arsenic, from getting into your drinking water supply. DEP staff have observed many cases of arsenic treatment media breakthrough.
  • The recommended arsenic treatment system is a Whole House two-tank adsorption system with the following components:
  1. Two Whole-House arsenic treatment tanks in series with a high capacity arsenic treatment media
  2. A sampling port between the two arsenic tanks
  3. A 5 micron sediment pre-filter before the arsenic tanks (depending on whether other water treatment elements are in place before the arsenic tanks)
  4. A 5 micron sediment post-filter after the arsenic tanks
  5. A water meter
An effective system also needs to be maintained. To qualify as a well maintained system, a water test must be conducted yearly from the kitchen sink and the sampling port between the two arsenic tanks.  If the arsenic between the tanks is greater than 5 mcg/l, your water treatment professional should remove the worker tank, replace it with the safety tank and install  a new safety tank.  
  • Test the treated water one or two weeks after the installation is complete. This is very important. Even the best water treatment professionals can make a mistake and your system may not be working due to an error. DEP staff have seen homes with the wrong media in the tank (pH adjustment media instead of arsenic treatment media). Good installations have been observed to not remove any arsenic for an entire year because of incorrect settings on the bypass valves. Hence the importance of the initial after-installation test.
  • After the initial testing shows the system is working, you should test the water at the kitchen sink and between the worker and the safety tanks (on a POE system) once every year.
  • There are three main options for arsenic water testing:
  1. Lab Sampling - Lab Testing: The most convenient option is to schedule someone from the lab to come out and collect the samples for arsenic testing.
  2. Water Treatment Company Sampling - Lab Testing: Some water treatment professionals will provide annual testing as part of their service. Obtaining a service contract from them will take the worry away from you and protect your family's health.
  3. Homeowner Sampling - Lab Testing: You can pick up the appropriate bottles from a convenient lab, collect the water samples yourself, and deliver them to the lab.
    • A list of certified labs capable of testing arsenic by the most sensitive analytical methods can be found on our "Testing Options" page.
    • Sampling instructions:
      • Stress the system: Run two cold water taps for at least ten minutes before collecting samples. This ensures the samples will not be from stale water inthe plumbing. See FAQ#24 for more details.
      • Collect the raw untreated water sample:
        • Locate where the water is coming into your home from the well. This is usually in the basement by the water pressure tank (usually blue). Run the water at the faucet next to your pressure tank (the faucet before any water treatment tanks) for one minute (or until it is clear if it is discolored). We suggest using a pan or bucket to collect the extra water. See the above photo.
        • Reduce the water flow at the pressure tank faucet to a low level.
        • Fill the bottle to any level between three quarters full and the neck of the bottle and/or follow any instructions provided by the lab.
      • Collect the between-the-tanks treated water sample:
        • This is the most important sample to collect when you have a two-tank Whole House system. See the picture below for the location:
      • Collect a sample of fully treated water at the kitchen sink:
        • Remember to keep two taps running for at least ten minutes while collecting the water samples to ensure the system is stressed properly and you do not test stale water from the plumbing or treatment tanks.
  • If arsenic is your only water quality problem, test for arsenic every year along with nitrates and total coliform which can change from year to year.
  • You don't need to purchase the full Private Well Testing Act (PWTA) package every year, but testing for all PWTA contaminants once every five years is recommended.
  • Yes, the treatment system needs to be stressed to be sure it works effectively when multiple taps are on at the same time.
  • To test Whole-House POE systems, you should run two cold water taps full blast for at least 10 minutes before collecting the sample between the tanks or at the klitchen sink.
  • The reason for stressing the system is that all treatment systems require contact time between the water and the treatment media to remove all the arsenic.  The more taps that are on at the same time in the home, the faster the water goes through the tanks, and this shortens the contact time.  You want to make sure the system is removing the arsenic during high water use times in the home (for example, two showers at one time, or a shower and the dishwasher or washing machine at the same time). 
  • Once per year you should test the water coming out of the kitchen tap. 
  • With a two-tank Point-of-Entry system you should also test the water between the two tanks once per year.
  • You can add a yearly recurring event to your electronic calendar to remind you that it is time to test your water.
  • You can pick a day of the year - maybe a holiday - and  always schedule your water test for that day each year. One person picked Valentine's Day for their water test reminder day saying "My love for my family reminds me to make sure they're not being exposed to arsenic."
  • It is much harder for arsenic treatment systems to remove arsenic when the pH of the water is greater than 8.5, and at high pH the life of the arsenic treatment media is greatly reduced.
  • In New Jersey wells with arsenic and a pH greater than 8.5, a pH adjustment tank should be included in their system.  This can be accomplished by installing an anion exchange system before the arsenic tanks. The anion exchange system will reduce the pH about one point. The anion exchange system may also remove some arsenic which will also help increase the life expectancy of the arsenic treatment media, but as we note in FAQ 16 we strongly recommend against relying on an anion exchange system to remove arsenic.
  • Well water with arsenic and pH greater than 9.5 is a more difficult situation that will require the attention and recommendation of your water treatment professional.  Injection of ascorbic acid into the water before it goes into the arsenic tanks is one example of an approach for dealing with very high pH water.
  • No. Unfortunately the only way to tell if your arsenic treatment system is working is by a water test. Because arsenic is colorless, odorless and tasteless you would not be able to tell if it is breaking through the treatment system by looking at, tasting or smelling your water.
  • All treatment systems require pre-treatment sediment filters to be changed on a regular basis. The timing of sediment filter changes depends on the specific characteristics of your well and water. If the water pressure in the home gradually drops, the first thing to look for is a clogged sediment filter. 
  • The post-treatment sediment filters will probaby only need to be changed once a year.
  • Your treatment system installer should take care of the proper disposal of used treatment media.
  • Used arsenic tanks shoud be tightly closed and disposed of.
  • Treatment installers should never "re-bed" (empty the used media and replace with new media) in your home.
  • Used media should not be touched with bare hands.